Southwest Airlines adds new fee to board early

The add-on fee trend among the nation's airlines continues as Southwest Airlines announced Monday a new $40 fee to let passengers board early.

Southwest, the nation's most popular domestic carrier, already charges $10 for its Early Bird Check-In service, which improves a passenger's position in the boarding queue.

But the new $40 fee guarantees that passengers get to be among the first 15 in line, letting them stow away carry-on bags in the overhead bin and pick seats with more legroom.

The new boarding option can be purchased at the gate, up to 45 minutes before boarding, and only when space is available, according to Southwest officials.

The fee was tested at the San Diego International Airport last month.

The fee is one of dozens that airlines began to add to regular fares in the past five years--so many that such fees now represent 10% to 30% of all revenue for most of the nation's largest airlines.

In 2012, the world’s biggest airlines collected a combined $36.1 billion in revenue for food, drinks, wireless Internet service, roomier seats and checked bags, among other charges, according to an industry analysis.